The present invention relates to flush valves that control the flow of water from toilet tanks to toilet bowls. More particularly it relates to canister flush valves.
Many systems for controlling the flush of toilet tank water to a toilet bowl are known, see e.g. U.S. Pat. Nos. 5,329,647 and 5,896,593. Such systems have a water inlet valve for the tank that is typically controlled by a float that senses tank water level. Depressing the trip lever moves a flush valve at the tank outlet so that water can empty from the tank through a vitreous pathway and into the bowl. As the tank water drains, the inlet valve float drops with the water level in the tank, thereby triggering inlet water flow. After sufficient tank water is drained, the flush valve closes so that the water level in the tank can be re-established. As the tank refills, the inlet valve float rises with the water and eventually closes the inlet valve to shut off the water supply.
A variety of flush valves have been devised for controlling the flow of water from the tank to the bowl. One of the most common in use today is the flapper type flush valve. Flapper flush valves have a pivotal yoke that supports a large diameter stopper that seals off the tank outlet until the trip lever is tripped to start a flush cycle. The large stopper is filled with air which slows its reseating until sufficient water has been drained from the tank. Another type of flush valve has a dedicated float that mounts a main seal. When the trip lever is depressed, the float is raised and the seal unseats to allow water to flow from the tank to the bowl. One flush valve of this type is referred to as a “canister” flush valve because the valve often has a large, generally cylindrical, float that resembles a can.
A concern common to many flush valves is creating and maintaining a tight seal at the tank outlet after the flush cycle is complete. The bulbous stoppers of flapper valves are generally initially good at achieving and holding a seal, but over time (e.g. years of operation) may permit leakage . Washer-like seals common in canister valves often have similar problems.
If the seal leaks, water will drain from the tank to the bowl. As the tank drains, the inlet valve float will fall and cause the inlet valve to open to refill the tank. If the leak persists, the inlet valve will remain open and water will continuously drain into the bowl. This will cause the bowl to overflow, or if the bowl has overflow passages, water will pass from the bowl to the building plumbing lines. Water is wasted in either case, which is very undesirable particularly given the emphasis local communities often place on the need for low water consumption toilets.
An example of a canister type flush valve is disclosed in U.S. Pat. No. 6,715,162 to Han et al. The disclosed flush valve has a valve body that mounts in the toilet tank at the outlet opening to the bowl defining a flow passage and an upper valve seat. The valve body also has an upright guide along which the float rides during a flush cycle. The float is a generally cylindrical hollow body with open ends, the upper end being above the water fill height of the tank. Water can flow through the inside of the float and through the valve body in the case of an overflow condition. The bottom end of the float has a groove about its circumference that retains a flat washer-type seal. The seal seats against the valve seat when the float is in its normal state in which the tank water is closed off from the outlet to the bowl.
Sealing problems with conventional canister flush valves, arise from various factors. The primary focus in achieving a good seal in prior devices is on how well the seal mates with the valve seat. While this is important, an often overlooked leak path arises at the float/seal interface. Particularly over time with material shrinkage or degradation of the seal, water may leak through the space between the seal and the float. This can become a low resistance leak path for water in the tank because the interface is typically a short, straight vertical path.
Regarding the contact of the sealing surface of the seal with the valve seat, again over time, it is possible for the seal to deform and take on a somewhat prolapsed configuration such that the seal does not mate properly with the valve seat. Thus, it is important that the seal be mounted to the float with sufficient backside (non-sealing side) support to prevent the seal from flexing away from the valve seat, without obstructing seating of the sealing side of the seal and while providing sufficient downward force on the seal so that a tight seal is maintained. Existing canister flush valves fail in one or more of these areas, and thus provide a less than optimal seal.
Another concern with flush valves is controlling the water consumption of the toilet. Water consumption is largely a factor of the amount of time in which the flush valve is open. For canister type flush valves, this is dependent upon the closure timing of the float, that is, the time it takes after the float is pulled from the valve body for the float to sink and reseat the seal. At least two factors affect the closure timing of the flush valve, namely the manner in which the floatation is achieved and the manner in which the float is caused to sink.
Many flush valves have an inverted cup-shaped float, with an open bottom and a closed top. When the float is pulled up by the flush trip lever, the inverted cup acts like a parachute and slows its descent by the frictional force of the water in the tank. U.S. Pat. No. 5,305,474 to Nardi et al. discloses a flush valve having such a float. Another common type of flush valve has an enclosed hollow vessel as the float. The air captured in the hollow vessel makes it buoyant so that it sinks slowly. U.S. Pat. No. 5,329,647 to Condon is an example of a flush valve with such a closed float. In both cases described above, the floats sink entirely under the force of gravity. The closure time of these valves is thus fixed for a given size and mass of the float.
The valve closure time can be adjusted by allowing water to flow into the float during the flush cycle. For example, as disclosed by U.S. Pat. No. 3,172,129 to Fulton et al., one or more small bleed holes can be made in an otherwise enclosed float, such as in the bottom wall of the float. When the float is pulled upward during a flush cycle, water in the tank can flow through the bleed holes into the interior of the float, thereby increasing the overall mass of the float and causing it to sink at an increased rate so as to shorten the closure time of the valve. The size and quantity of the openings can be selected to achieve a closure rate that corresponds to a desired water consumption.
One problem, however, with the use of bleed holes is that immediately after the float is moved, the pressure head in the tank is relatively high such that water will rush into the bleed holes quickly. If, unlike in the valve disclosed by Fulton et al., the float is not enclosed at the top, the rapid flow of water through the bleed holes can spray up through the float and against the underside of the tank lid. This is disadvantageous for several reasons, but primarily because of the possibility of the water spraying out the tank, or leaking down around on the rim of the tank, and onto the bathroom floor.
Thus, a need exists for an improved canister type flush valve that provides for better valve closure control and effects a better seal at the tank outlet.